Shock wave lithotripsy (SWL) is a non-invasive treatment for kidney stones and other ailments. However, current lithotripters produce painful side effects, and the mechanisms of lithotripsy and the causes of the side effects are not fully understood. Electrohydraulic lithotripters (EHL's), which use an underwater spark as a shock wave source, had been the treatment of choice but use has declined because the shocks are inconsistent, cause painful side effects and the electrodes are short lived. Typically, the electrode head wears out during a procedure, and must be replaced before completing the procedure. New types of lithotripters are more consistent and last longer than one procedure, but their clinical outcomes are reduced and side effects are greater. Phase I showed the feasibility of using a wire-initiated sparker to produce consistent and precise shocks, of controlling the shock (for potential improved comminution of kidney stones and reduction in side effects), of lasting for many procedures. The proposed Phase II continues research towards the long-term goal to develop a new commercial EHL that exceeds the clinical outcomes of lithotripters, with reduced side effects, much longer life and lower cost. The specific project objectives are to develop a wire feed system needed to employ wire- initiated sparkers for EHL, demonstrate ultra-long lifetime using the wire-feed, map out the acoustic field of the shock and cavitation in the focal region, conduct research using the sparker's varied shock waveforms to improve comminution of kidney stones and develop a prototype wire-feed sparker for commercialization. A successful project will result in improved clinical results of SWL at reduced cost. Shock wave lithotripsy (SWL) is a non-invasive treatment for kidney stones and other ailments. The electrodes in current systems must be replaced during a procedure, and the results are inconsistent, with unpleasant side effects. A successful program will result in a new SWL system with electrodes lasting several procedures, more consistent clinical outcomes, reduced side effects and lower cost.